JPH03250549A - Metal vapor electric discharge lamp - Google Patents

Abstract

PURPOSE:To have a discharge lamp whose output does not drop even after a long time of lighting, by encapsulating a certain specific amount of metal Tl or halide Tl in the discharge lamp. CONSTITUTION:An amount of Hg sufficient for maintaining arc discharge, a rare gas, an appropriate amount of Fe, and halogen are encapsulated in a light emitting tube 1 equipped with electrodes 2. Thus a metal vapor discharge lamp is accomplished. In this discharge lamp, metal Tl or halide Tl is encapsulated so that the Tl ratio in gram atom to Fe becomes 1/200 thru 1/2. This prevents formation of this film caused by Fe attachment to the inner wall of the light emitting tube, and the ultraviolet output can be maintained for a long time. Lessening of the Tl addition from the above-mentioned ratio lessens the effect of hindering Fe attachment to the inner wall, while increasing from the ratio weakens the light emission spectrum due to Fe.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a metal vapor discharge lamp used for photochemical reactions, curing of paints and inks, and the like.

[Prior art and its problems]

Ultraviolet rays are often used to cause photochemical reactions and to cure paints, inks, etc., and for these purposes, ultraviolet rays with a wavelength range of about 280 to 400 nm are effective.

Conventionally, high-pressure mercury lamps have been used as sources of ultraviolet rays, but the light emitted from high-pressure mercury lamps consists of a large number of bright line spectra, and each spectrum is dispersed over a fairly wide wavelength range. There are problems with the efficiency of using high-pressure mercury lamps for photochemical reactions and paint curing, etc., which have an effective wavelength range of . For this reason, metal vapor discharge lamps are often used in which a metal halide is sealed as a luminescent substance in the arc tube of a high-pressure mercury lamp to increase the amount of light emitted in an effective wavelength range. In particular, metal vapor discharge lamps filled with iron continuously emit light in the wavelength range of 350 to 400 nm, and are therefore convenient for purposes such as photochemical reactions and curing of paints.

However, when a metal vapor discharge lamp containing iron is left on for a long time, iron adheres to the inner wall of the arc tube and forms a thin film. Therefore, there is a problem in that the amount of iron that contributes to light emission decreases, and the formed thin film obstructs the transmission of ultraviolet rays, resulting in a decrease in the output of ultraviolet rays.

In order to improve this problem, it is known to further add lead to a metal vapor discharge lamp containing iron. but,
Adding lead can achieve the original purpose of preventing the formation of a thin film of iron and maintaining ultraviolet output, but at the same time, the button significantly weakens the output of mercury's large emission line spectrum of 302, 313, and 365 nm. It is not often used for purposes such as photochemical reactions or curing of paints because it is exposed to light, and tin is also known to be added, but this also reduces the output of the bright line spectrum of mercury, just like buttons. There is a problem that the performance is significantly reduced.

[Purpose of the invention]

Therefore, an object of the present invention is to provide a metal vapor discharge lamp that prevents iron from adhering to the inner wall of the arc tube and maintains ultraviolet output for a long time without adversely affecting the emission spectrum of mercury and iron. It is something.

[Configuration of the Invention and Its Effects] The configuration of the present invention is based on a metal arc tube with an electrode, in which an appropriate amount of iron and halogen is sealed together with sufficient amounts of mercury and rare gas to maintain arc discharge. In a steam discharge lamp, metal thallium or thallium halide is used at a gram atomic ratio of 1/200 to 1/2 of thallium to iron.
It is characterized in that it is sealed to prevent iron from adhering to the inner wall of the arc tube and forming a thin film.

That is, the inventors discovered that halides of thallium (TI) were effective in achieving the above object, and completed the present invention after conducting various experiments. Addition of thallium chloride at a gram atomic ratio of 1/200 to 1/2 of thallium to iron can prevent iron from adhering to the inner wall of the arc tube and forming a thin film, thereby prolonging the ultraviolet output. Can keep time. Note that if the amount added to iron is less than 1/200 in terms of gram atomic ratio, the effect of preventing iron from adhering to the inner wall of the arc tube will be small and the ultraviolet output will not be maintained sufficiently; If it exceeds this, there will be a problem that the emission spectrum due to iron will become slightly weaker.

〔Example〕

Embodiments of the present invention will be specifically described below based on the drawings.

Figure 1 shows a metal vapor discharge lamp with a rated power consumption of 4KW used as a light source for photochemical reactions, and whose inner diameter is 22cm.
A pair of electrodes 2,
2 are arranged facing each other, and the distance between the electrodes is 250 mm. 6 Arc tube 10 Both ends are seal portions 11;
1 is sealed with a molybdenum foil 3, and an outer conductor 4 and an electrode 2 are electrically connected via this molybdenum foil 3. Inside the arc tube 1, 120+eg of metallic mercury, 13mg of mercury iodide, 3.5mg of iron, 1,1+mg of thallium iodide, and 30mmHg of xenon gas are sealed. The amount of thallium added is 1/19 in gram atomic ratio to iron.

When this metal vapor discharge lamp was lit, the lamp power was 4
At KW, the lamp current was 12.5A and the lamp voltage was 355V. Although the lamp was lit for up to 1000 hours, no iron adhered to the inner wall of the arc tube 1, and no thin iron film was formed. At this time, the wavelength range is 280 to 400n+m
As shown in characteristic curve A in Figure 2, the output maintenance rate for 1000 hours was 9.
It was 0%.

Incidentally, when a metal vapor discharge lamp similar to this example but without thallium added was lit for comparison, iron began to adhere to the inner wall of the arc tube 1 after several tens of hours had passed, and a thin film formed. was formed. The output maintenance rate decreased to 50% after 1000 hours, as shown by characteristic curve B in FIG.

Next, we investigated the effect of adding thallium on the output of the mercury emission line spectrum and the output of the iron spectrum, and found that the metal vapor discharge lamp of this example was significantly better than the one without the addition of thallium. , the spectral power of mercury decreased by 3%, and the spectral power of iron decreased by 5%, the decreases were small. On the other hand, when lead or tin was added and sealed instead of thallium in this example, the spectral output of mercury decreased by 35% when lead was added, and by 28% when ta was added.
It was confirmed that thallium has little negative effect on the spectral output of mercury.

Further, the addition of thallium has almost no effect on electrical characteristics such as starting power and restriking voltage.

In this example, metallic iron and thallium halide are added, but they may be added as iron halide and metallic thallium, or a mixture of both may be added to obtain the same effect.

〔Effect of the invention〕

As explained above, in the present invention, thallium is doped in a metal vapor discharge lamp doped with iron so that the gram atomic ratio of thallium to iron is 1/200 to 1/2. Thallium has almost no negative effect on the emission spectrum output of mercury and iron, and the properties of mercury and iron can be utilized as they are. Since iron is prevented from adhering to the inner wall of the arc tube and no thin film is formed, the output of ultraviolet rays in the wavelength range of 280 to 400 nm does not decrease even when the lamp is turned on for a long time. Therefore, the metal vapor discharge lamp can be suitable as an ultraviolet source for causing photochemical reactions and curing paints, inks, and the like.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a metal vapor discharge lamp, and FIG. 2 is an explanatory diagram of the characteristics of the output maintenance rate.

Claims (1)

[Claims] A metal vapor discharge lamp in which an arc tube equipped with electrodes is filled with sufficient amounts of mercury and rare gas to maintain arc discharge, as well as appropriate amounts of iron and halogen, including metal thallium or metal thallium. It is characterized in that thallium halide is sealed so that the gram atomic ratio of thallium to iron is 1/200 to 1/2, thereby preventing iron from adhering to the inner wall of the arc tube and forming a thin film. Metal vapor discharge lamp.